The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An engine generates rotary force by the combustion of fuel and the remainder is discharged as thermal energy. In particular, coolant absorbs the thermal energy while being circulated through the engine, a heater, and the radiator and releases the absorbed thermal energy to the outside.
When a temperature of the coolant of the engine is low, viscosity of oil increases and friction force tends to thus increase, fuel consumption tends to increase, the temperature of exhaust gas slowly increases, an activation time of a catalyst is lengthened, and the quality of the exhaust gas may deteriorate. Moreover, a time when a function of a heater is normalized may be lengthened.
When the coolant temperature of the engine is excessive, knocking occurs and in order to suppress the knocking, an ignition time is controlled, and as a result, performance may deteriorate. Further, when the temperature of a lubricant is excessive, lubrication may deteriorate.
Therefore, one coolant control valve unit is applied, which controls multiple cooling elements through one valve, such as keeping the coolant at a high temperature at a specific portion while keeping the coolant at a low temperature in other portions.
The coolant control valve unit controls the coolant which is circulated through each of the engine (an oil cooler, the heater, an EGR cooler, and the like) and the radiator to improve overall cooling efficiency of the engine and reduce the fuel consumption.
Therefore, the coolant temperature at a predetermined location is sensed by using the coolant temperature sensor, a target coolant temperature is set according to a driving condition, and the coolant control valve unit is controlled according to the target coolant temperature.
In particular, a method may be used, which arranges the coolant temperature sensors sensing the coolant temperatures at a coolant inlet side and a coolant outlet side of the engine and an outlet side of the radiator and controlling valve opening rate of the coolant control valve unit according to the coolant temperature sensed by the coolant sensors.
Meanwhile, research has progressed, which minimizes the number of the coolant temperature sensors, senses the coolant temperature at a predetermined location by using the already arranged coolant temperature sensor, calculates the coolant temperature at the predetermined location, and rapidly changes valve opening rate of the coolant control valve unit when the target coolant temperature is changed by using the sensed coolant temperature and the calculated coolant temperature.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.